Damage free enhancement of dopant diffusion into a substrate

ABSTRACT

A method of doping a substrate. The method may include implanting a dose of a helium species into the substrate through a surface of the substrate at an implant temperature of 300° C. or greater. The method may further include depositing a doping layer containing a dopant on the surface of the substrate, and annealing the substrate at an anneal temperature, the anneal temperature being greater than the implant temperature.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to, and is a continuation of U.S.patent application Ser. No. 15/412,837, filed Jan. 23, 2017, entitled“DAMAGE FREE ENHANCEMENT OF DOPANT DIFFUSION INTO A SUBSTRATE” whichclaims priority to and is a continuation of U.S. patent application Ser.No. 14/977,849, filed Dec. 22, 2015, entitled “DAMAGE FREE ENHANCEMENTOF DOPANT DIFFUSION INTO A SUBSTRATE.” U.S. patent application Ser. No.15/412,837 and U.S. patent application Ser. No. 14/977,849 areincorporated herein by reference in their entirety.

FIELD

The present embodiments relate to methods of improving diffusion, andmore particularly to methods of doping a substrate.

BACKGROUND

As semiconductor devices such as logic and memory devices continue toscale to smaller dimensions, the use of conventional processing andmaterials to fabricate semiconductor devices is increasinglyproblematic. In one example, new approaches for doping semiconductorstructures are being investigated to supplant ion implantation. Forexample, in doping device structures where the smallest devicedimensions are on the order of 20 nm or below, residual damage caused byion implantation may be unacceptable. Accordingly, techniques such asdoping a target region of a substrate by thermally-driven outdiffusionfrom a deposited layer have been explored. As currently practiced, thisapproach may be limited due to thermal budget considerations in theamount of dopant incorporated into the target region as well as theactivation of dopant.

With respect to these and other considerations the present disclosurehas been provided.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form further described below in the Detailed Description.This Summary is not intended to identify key features or essentialfeatures of the claimed subject matter, nor is the summary intended asan aid in determining the scope of the claimed subject matter.

In one embodiment, a method of doping a substrate may include implantinga dose of a helium species into the substrate through a surface of thesubstrate at an implant temperature of 300° C. or greater. The methodmay further include depositing a doping layer containing a dopant on thesurface of the substrate; and annealing the substrate at an annealtemperature, the anneal temperature being greater than the implanttemperature.

In another embodiment, a method of doping a semiconductor device mayinclude implanting a dose of helium into a substrate through a surfaceof the substrate at an implant temperature above 300° C., the dose ofhelium comprising 5E15/cm² or greater. The method may further includedepositing a doping layer containing a dopant on the surface of thesubstrate, the doping layer having a thickness less than 1 nm; andannealing the substrate at an anneal temperature greater than 600° C.

In another embodiment, a system for doping a substrate may include atransfer chamber to house and transfer a substrate; a hot implantchamber coupled to a helium source and coupled to the transfer chamber.The hot implant chamber may include a plasma generator generating heliumions, and a substrate heater generating a substrate temperature of 300°C. or more. The system may further include a dopant deposition chambercoupled to a dopant source and to the transfer chamber, the dopantdeposition chamber providing dopant to the substrate. The system mayalso include an annealing chamber coupled to the transfer chamber andhaving a heater generating a substrate temperature of at least 600° C.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1H illustrate exemplary features involved in processing asubstrate according to embodiments of the disclosure;

FIG. 2 shows the results of secondary ion mass spectrometry (SIMS)measurements of silicon substrates, illustrating the effect of heliumimplantation on dopant incorporation;

FIGS. 3A-3C present cross-sectional electron micrographs of samplesillustrating the effect of helium ion implantation;

FIG. 4A shows general features of a finFET device in cross section,while FIG. 4B shows a close-up of a portion of the structure of FIG. 4Aaccording to embodiments of the disclosure;

FIG. 5 depicts an example of a processing apparatus according toembodiments of the disclosure; and

FIG. 6 depicts an exemplary process flow.

DETAILED DESCRIPTION

The present embodiments will now be described more fully hereinafterwith reference to the accompanying drawings, where some embodiments areshown. The subject matter of the present disclosure may be embodied inmany different forms and are not to be construed as limited to theembodiments set forth herein. These embodiments are provided so thisdisclosure will be thorough and complete, and will fully convey thescope of the subject matter to those skilled in the art. In thedrawings, like numbers refer to like elements throughout.

In the present embodiments, the present inventors have identified novelapproaches to promote dopant diffusion into a substrate without damageto the substrate. In various embodiments, a dose of helium may beimplanted into a substrate when the substrate is at an implantationtemperature in a temperature range above room temperature. The dose ofhelium may be provided in conjunction with deposition of a dopantmaterial on the substrate in a manner resulting in improved diffusion ofthe dopant into the substrate, activation of the dopant within thesubstrate, while not generating residual defects within the substrate,resulting in a damage-free enhancement of diffusion.

FIGS. 1A-1H illustrate exemplary features involved in processing asubstrate according to embodiments of the disclosure. In someembodiments, the operations illustrated in FIGS. 1A-1F may be performedin different processing tools, while in other embodiments, theoperations may be performed within a given integrated tool havingmultiple process chambers to perform different operations, such as acluster tool. Turning in particular to FIG. 1A, there is shown a firstinstance where a substrate 102 is provided. In various embodiments, thesubstrate 102 may be a semiconductor material, such as silicon,germanium, silicon carbide (SiC), or a silicon:germanium alloy. In otherembodiments, the substrate may comprise a known group III-V compoundsemiconductor (e.g., GaAs, InGaAs) or group II-VI compound semiconductor(e.g., CdTe). In particular, the substrate 102 may generally have amonocrystalline structure characterized by a crystalline lattice asknown in the art. The embodiments are not limited in this context. Whilethe substrate 102 is shown as having a planar configuration, in variousembodiments, the substrate 102 may include features presenting surfacesextending at different angles with respect to one another, such as athree dimensional (3D) transistor device. Examples of 3D devices includefin field effect transistor devices (finFET), gate-all-around (GAA)transistor devices, horizontal GAA devices (HGAA), and other devices.The embodiments are not limited in this context. In the example of FIGS.1A-1F, doping of a particular region of the substrate 102. In differentembodiments, the doping operations may be representative of an isolationregion of a transistor, a source/drain extension region, or asource/drain contact region, to name a few regions.

As shown in FIG. 1A, the substrate 102 may include a surface layer 104to be removed before doping. The surface layer 104 may be a native oxideor chemical oxide layer in some instances. In various embodiments, thesurface layer 104 is exposed to an etchant 106. In one example, theetchant 106 represents species obtained from a hydrogen plasma, wherethe etchant impinges upon the substrate 102 while the substrate 102 isheld at low pressure. Heat 108 may be applied to the substrate 102 toelevate the substrate temperature to a target range to promote etchingof the surface layer 104. In one example for etching an oxide layer on asilicon substrate, the substrate 102 may be subject to etching by ahydrogen plasma at a substrate temperature between 400° C. and 500° C.,and in particular, at a substrate temperature of 450° C. The duration ofthe exposure may be adequate to remove the surface layer 104. In otherembodiments, other known etchants for etching an oxide may be employed.

Turning now to FIG. 1B, there is shown an implantation operation, wherethe implantation operation may be performed subsequently to theoperation shown in FIG. 1A. In some examples, the implantation operationis performed after the etch operation of FIG. 1A, while the substrate102 is not exposed to ambient atmosphere between the operations of FIG.1A and FIG. 1B. In various embodiments, the substrate 102 is exposed tohelium species 114, where the helium species 114 are directed to thesurface 110. In this example, the surface 110 may be exposed after theremoval of the surface layer 104. The helium species 114 may be directedto the surface 110 of substrate 102 at a target energy and target doseto promote a subsequent doping process. The helium species 114 may, forexample, comprise helium ions having an energy of 500 eV to 5000 eV, andmay be directed to the substrate 102 in a dose comprising 5E15/cm² to1E17/cm² He. The embodiments are not limited in this context.

As further shown in FIG. 1B, heat 112 may be supplied to the substrate102 during exposure to the helium species 114. In various embodiments,the helium species 114 are implanted into the substrate 102 throughsurface 110, while the substrate 102 is heated to maintain an implanttemperature above room temperature (25° C.). For example, in variousembodiments, the implant temperature may range above 300° C. and may, inparticular, range between 300° C. and 600° C. In particular embodiments,the implant temperature may be set in a range between approximately 400°C. and approximately 500° C. The embodiments are not limited in thiscontext.

Turning now to FIG. 1C, there is shown an instance of the substrate 102after the operation of FIG. 1B. An altered layer 120 may be formed inthe substrate 102 adjacent the surface 110. As detailed below, thealtered layer 120 may enhance doping of the substrate 102 by promotingdopant diffusion across the surface 110. In particular, the alteredlayer 120 may enhance doping of the substrate without introducingresidual damage into the substrate after a doping process is complete.

Turning now to FIG. 1D, there is shown an operation where a doping layer122 is deposited on the surface 110 of the substrate 102. In thisexample, the doping layer 122 is deposited after the altered layer 120is formed, while in some embodiments, the doping layer 122 may bedeposited before the implantation of helium is performed to create thealtered layer 120. In various embodiments, the doping layer 122 may beformed on the substrate 102 after the implantation of helium withoutexposing the substrate 102 to ambient atmosphere. The doping layer 122may include an appropriate dopant for doping the substrate 102, such asarsenic, boron, phosphorous, or silicon. The embodiments are not limitedin this context. The doping layer 122 may be deposited using knowntechniques such as chemical vapor deposition. The doping layer 122 maybe deposited at an appropriate thickness for creating a target dopedregion within the substrate 102. In some embodiments, the doping layer122 may have a thickness of between 0.1 nm and 3 nm. The embodiments arenot limited in this context. As an example, a 0.1 nm thick layer of Asmay be useful to dope a target region of the substrate 102, such as a 10nm thick region, to an appropriate level.

Turning now to FIG. 1E, there is shown an operation subsequent to theoperation of FIG. 1D. In this operation, a capping layer 124 isdeposited on the doping layer 122. The capping layer 124 may be usefulto aid in dopant retention during subsequent processing performed todrive in dopant from the doping layer 122 and to activate the dopant.The capping layer 124 may be formed of a material appropriate for useduring high temperature dopant annealing, as known in the art, such assilicon nitride. The capping layer 124 may be deposited at roomtemperature, for example, to minimize dopant movement before subsequentprocessing. In some examples, the capping layer 124 may be formed afterformation of the doping layer 122 without exposing the substrate 102 toambient atmosphere in the meantime.

Turning now to FIG. 1F, there is shown a subsequent operation where thesubstrate 102 is subject to high temperature annealing to drive in thedopant and activate the dopant of doping layer 122. This is shownschematically by the provision of heat 126 to the substrate 102.Examples of appropriate anneal temperature may vary with dopant type, aswell as type of semiconductor material. Some examples of appropriateanneal temperatures for annealing silicon substrates are temperatures ofgreater than 800° C., such as 900° C. to 1000° C. Some examples ofappropriate anneal temperatures for annealing semiconductor substratesother than silicon, such as group III-V compound semiconductorsubstrates, are temperatures of 600° C., 700° C., or greater. Annealingmay take place via furnace annealing or using rapid thermal processingequipment, as known in the art. The duration of an activation anneal mayvary according to the anneal temperature, for example, the duration maydecrease with increased anneal temperature. Performing of a rapidthermal anneal may be especially useful to drive in and activate dopant,where the anneal time at a set temperature is less than 10 seconds. Theembodiments are not limited in this context. For example, a rapidthermal anneal may be performed where the substrate is heated from roomtemperature to a target temperature at a target heating rate, where arate of temperature increase is 50° C./s or greater. The embodiments arenot limited in this context. In the case of silicon substrates, thetarget temperature for such a rapid thermal anneal may be 900° C., 950°C., or 1000° C. The embodiments are not limited in this context.

As schematically illustrated in FIG. 1F, the annealing at elevatedtemperature may generate diffusing dopant 128, shown by the downwardarrows. The diffusing dopant 128 may diffuse into the altered layer 120.In addition, the diffusing dopant 128 may settle within certain siteswithin the crystalline lattice of the substrate 102. In particular, thediffusing dopant 128 may diffuse into active sites provided in thealtered layer 120. As further shown in FIG. 1F, outdiffusing dopant 129may diffuse outwardly toward the capping layer 124. The relative amountof the outdiffusing dopant 129 may differ from the amount of diffusingdopant 128. The relative amount of outdifusing dopant may also vary withthe composition of the capping layer 124. For example, arsenic maydiffuse more rapidly into an oxide capping layer, while not diffusing asreadily into a nitride capping layer.

In some embodiments, the operation of FIG. 1E may be omitted, whereannealing as generally discussed with respect to FIG. 1F takes placewithout a capping layer. In such cases, a portion of dopant in thedoping layer 122 may evaporate from the substrate 102.

Turning now to FIG. 1G, there is shown a subsequent instance after theannealing operation of FIG. 1F. At this stage the substrate 102 includesa doped layer 132 adjacent the surface 110. The capping layer 124 mayalso retain some dopant. In a subsequent operation, shown in FIG. 1H,the capping layer 124 may be removed, for example, by a known selectiveetching process appropriate for the given material of the capping layer124. A highly doped region, shown as the doped layer 132 may be incondition for further processing. For example, in embodiments where thedoped layer 132 forms in a source/drain region, a metal contact, such asa silicide, may be subsequently formed to contact the substrate 102 inthe region of the doped layer 132.

In accordance with various embodiments, the doped layer 132 may have aconcentration of active dopants higher than the level achieved by knownprocessing techniques. By providing a hot helium implant into thesubstrate 102 before driving dopants into the substrate 102, the alteredlayer 120 may promote diffusion of dopant across the interface formed atsurface 110.

In exemplary experiments, the present inventors have discoveredimplantation conditions for preparing a substrate before introduction ofdopants, where the implantation conditions substantially enhancediffusion of dopants across a substrate interface as well as activationof dopants, in comparison to known processing techniques. FIG. 2 showsthe results of secondary ion mass spectrometry (SIMS) measurements ofsilicon substrates, illustrating the effect of helium implantation ondopant drive-in. A series of curves are shown representing depthprofiles of As with respect to a surface of silicon (0 nm depth) forvarious different experimental conditions. In all examples, a <1 nmlayer of As is deposited on a surface of monocrystalline silicon beforea rapid thermal anneal is performed at 1000° C. for 5 s. Curve 204represents a control condition where no helium is implanted into thesubstrate. As shown, the curve 204 shows a distribution of arseniclocated close to the surface of the silicon. For example, the peakconcentration is about 5 E20/cm² and the depth where the concentrationreaches 1E18/cm² is approximately 13 nm. The total retained dose ofarsenic in this example is 2.63E14/cm². The curve 202 represents thedistribution of arsenic when a room temperature helium implant isperformed to a dose of 1E15/cm² at an ion energy of 1 keV beforedeposition of arsenic and subsequent annealing. In this example, thedepth at 1E18/cm² As concentration is 12 nm, while the total retaineddose is 2.5E14/cm². This result indicates room temperature heliumimplantation at a level of 1E15/cm² is not effective in increasingarsenic diffusion into the substrate as compared to no implantation. Thecurve 206 represents the distribution of arsenic when helium isimplanted at room temperature to a dose of 1E16/cm² before arsenicdeposition and annealing. In this example, the implantation of heliumresults in a total retained dose of arsenic of 7.25 E14/cm² afterannealing, a nearly 3-fold increase in retention as opposed to zero dosehelium implantation or 1E15/cm² helium implantation. Disadvantageously,the curve 206 exhibits a tail at depths greater than 12 nm below thesurface, where the tail has a shallower slope than in other cases. Theconcentration of As does not drop to 1E18/cm² until a depth ofapproximately 18 nm below the surface.

The curve 208 represents the As concentration after a helium implant isperformed in accordance with embodiments of the disclosure. In thisexample, the helium is implanted at 450° C. to a dose of 1E16/cm2 beforearsenic deposition and annealing. In this example, the implantation ofhot helium results in a total retained dose of arsenic of 5.09 E14/cm²after annealing, a 2-fold increase in retention as opposed to zero dosehelium implantation or 1E15/cm² helium implantation. The slope ofconcentration of As vs depth is similar to the curve 202 and curve 204,while the concentration reaches 1E18/cm2 at a depth of approximately 18nm below the surface.

Sheet resistance measurements were additionally performed on the samplescorresponding to curves 202-208 after implantation, arsenic deposition,and annealing. In the case of no helium implant corresponding to curve204, the sheet resistance was too high register according to the surfaceprobe measurement. In the case of room temperature helium implantationto a dose of 1E15/cm², corresponding to curve 202, the measured Rs is22,000 Ohm/Sq. This resistance value is indicative of incompleteactivation of the arsenic incorporated in the silicon substrate. Inother words, for a retained arsenic dose of 2.5E14/cm², when a highfraction of the retained arsenic dose, such as 50% is activated, a sheetresistance substantially lower than 22,000 Ohm/Sq is expected. In thecase of room temperature helium implantation to a dose of 1E16/cm²,corresponding to curve 206, the measured Rs is 3,500 Ohm/Sq. Thisresistance value is also indicative of incomplete activation of thearsenic incorporated in the silicon substrate. In other words, for aretained arsenic dose of 7.25E14/cm², when a high fraction of theretained arsenic dose, such as 50% is activated, a sheet resistancesubstantially lower than 3,500 Ohm/Sq is expected. In the case of 450°C. helium implantation to a dose of 1E16/cm², corresponding to curve208, the measured Rs is 300 Ohm/Sq. This resistance value is indicativeof a much higher activation of the arsenic as compared with the samplecorresponding to curve 306, where the same helium dose is implanted atroom temperature. As a rough estimate for hot helium implantation at1E16/cm² dose, the activation of Arsenic may be improved byapproximately a factor of 10 or so with respect to the correspondingroom temperature helium implantation. In particular, while the retainedamount of arsenic after annealing is somewhat less (5E14/cm²) ascompared to a room temperature helium implantation dose of 1E16/cm² theresistance is reduced by a factor of 12. In various embodiments, anactivation level of the dopant in the substrate may be at least fivetimes more than a second activation level of the dopant in the substratewhen the implant temperature is room temperature.

FIG. 3A, FIG. 3B, and FIG. 3C present cross-sectional electronmicrographs of samples corresponding to curve 202, curve 206, and curve208, respectively. As shown in FIG. 3A, where a substrate 312 isimplanted with 1E15/cm² helium dose at room temperature before arsenicdrive-in annealing, a high concentration of defects 316 (dark regions)is visible near the surface 314, where defects also extend further belowthe surface 314. In FIG. 3B, where the substrate 322 is implanted with1E16/cm² helium dose at room temperature before arsenic drive-in, largesize defects 326 are visible near the surface 324, with defects alsoextending further below the surface 324. In FIG. 3C, where the substrate332 is implanted with 1E16/cm² helium dose at 450° C. before arsenicdrive-in, no defects are visible in a region 336 near the surface 334.Additionally, the substrate 332 does not exhibit visible defects atdistances further below the surface 334.

Without limitation as to any particular mechanism, the increaseddiffusion of dopant into the semiconductor substrate and improvedactivation of the dopant may be the result of a combination of featuresinduced by hot helium implantation. For one, hot helium implantation mayintroduce vacancies within the semiconductor lattice of amonocrystalline semiconductor material such as silicon. At anappropriate temperature range, such as 300° C. to 500° C., and at heliumimplanted doses, such as the range of 5 E15/cm²-1E17/cm² at an ionenergy in the range of 200 eV to 20 keV, a high concentration ofvacancies may be introduced into the crystalline lattice just below asurface of the crystalline substrate without generating an amorphousregion. These vacancies may act to increase diffusion of dopant into thecrystalline lattice for thermally diffusing dopants, while alsoproviding sites for activation of dopants.

By maintaining the substrate temperature at a sufficiently high levelduring implantation, formation of an amorphous layer may be avoided,even when the substrate is exposed to a large dose of helium, such as1E16/cm² or more. As a non-limiting example, a dose of 1E17/cm² heliummay be directed to a substrate at a temperature in excess of 450° C. Ata substrate temperature of 450° C., after implantation with a dose of1E17/cm² helium, while at a substrate temperature of 500° C., anestimated helium dose up to 2E17/cm² may be implanted into a substratewhile not inducing residual damage. The avoidance of an amorphous layeras-implanted may also avoid unwanted defect formation occurring insubstrates implanted at low temperature, after high temperatureannealing is performed to drive in and activate dopant, and torecrystallize the amorphous regions. Recall from FIG. 2 and FIG. 3Bwhere room temperature implantation of 1E16/cm² helium results in arelatively large amount of retained arsenic dopant (7.25 E14/cm²) aftera drive-in anneal, while the samples show residual defects and much lessactivation of dopant than for samples implanted at 450° C. with the samedoes of helium.

Additionally, by maintaining the substrate temperature below atemperature range where defects are substantially annihilated, thebenefits of vacancy creation in terms of enhanced diffusion andactivation may be preserved. For example, when substrate temperature ismaintained above 550° C. to 600° C., vacancies and interstitial defectsmay combine at a rapid rate during the high temperature implantation,resulting in a much lower number of residual vacancies present after theimplantation process is complete.

Another feature of maintaining implantation temperature in a range ofapproximately 300° C. to 500° C. during helium implantation, is theability to drive out helium dynamically during the implantation process.In this manner the concentration of helium remaining after hightemperature implantation may be minimal.

In various embodiments, the operations generally outlined in FIGS. 1A-1Hmay be applied to improve contact resistance in a 3D device such as afinFET. FIG. 4A shows general features of a finFET device 400 in crosssection, before a doping process for forming contact regions to asource/drain of the finFET. FIG. 4B shows a close-up of a portion of thestructure of FIG. 4A at an instance generally corresponding to FIG. 1E.In particular, in FIG. 4A, fin structures shown as the fins 402 havebeen formed from a substrate base region 406 according to knowtechniques. Isolation 408 is also formed between fins 402, wherein justtop portions of fins 402 are exposed. The top portions of the fins 402may be used as source/drain regions to be contacted by a contactmaterial, by introduction of an appropriate level of doping into thefins 402. For advanced technology nodes, such as nodes where the spacingbetween adjacent fin structures is 15 nm or less, doping by thermaldiffusion of a deposited doping layer, such as a film containing adopant, may be useful to avoid excessive defect formation created whenusing ion implantation to dope the fins. Accordingly, in accordance withembodiments of the disclosure, the operations of FIGS. 1A-1E may beapplied to prepare the fins for doping.

A result of the improved activation and diffusion provided by hightemperature helium implantation (see FIG. 1B) is the ability to use athinner dopant layer to serve as a source of dopant for the fins. Forexample, a 0.1 nm arsenic layer may provide sufficient amount of arsenicto reach a target arsenic incorporation and dopant activation level forforming a low contact resistance contact in a narrow fin where the widthW is 20 nm or less. This thinner layer of arsenic used in the presentembodiment contrasts with known techniques performed without using a hothelium operation, where the known techniques may use an arsenic layerthickness in the range up to 2 nm, to compensate for less efficientactivation of arsenic, as discussed above.

A consequence of the use of a thinner dopant layer afforded by thepresent embodiments, is the increased scalability of doping by diffusionfrom a dopant layer as the pitch between adjacent fins is reduced. Forexample, referring in particular to FIG. 4B, the annealing process forperforming doping of a fin may specify a minimum thickness of a cappinglayer, such as 2 nm, to ensure proper drive-in of dopant and to keepdopant loss during annealing at an acceptable level. To use one example,the spacing S between the sidewalls 404 of adjacent fins, i.e, fins 402,may be 7 nm. As further shown in FIG. 4B, a doping layer 412 has formedon the sidewalls 404 of fins 402. The doping layer 412 is to be used asa doping source of the fins 402 by driving in dopants of the dopinglayer 412 across the surface of the sidewalls 404 and into the body ofthe fins 402. In one example, the doping layer 412 may be a layer ofarsenic and the thickness T of the doping layer 412 may be 0.1 nm.Accordingly, a distance D separating adjacent dopant layers along thehorizontal direction may be approximately 6.8 nm. In this scenario, acapping layer 410 having a thickness (along the horizontal direction) of2 nm may readily be formed along two adjacent sidewalls, sidewalls 404.If the thickness T of doping layer 412 is specified to be 2 nm as in aconventional process, D is then 3 nm (=7 nm−2 nm−2nm). In this latterscenario, forming a capping layer 410 of thickness 2 nm between twoadjacent fin sidewalls may be problematic. Moreover, further scaling tosmaller fin separation, such as 5 nm, may be precluded by the lack ofspace to accommodate 2 nm thick dopant layers and 2 nm thick cappinglayers.

In accordance with different embodiments, the process window forachieving enhanced dopant diffusion and activation using hot heliumimplantation may vary according to implantation ion energy, as well assubstrate material. For example, the best implantation temperature forimplanting helium may vary between silicon and silicon:germaniumsubstrates. Moreover, while examples of arsenic doping are detailedherein, the present embodiments cover doping using other dopantmaterials including p-type dopants such as boron.

FIG. 5 depicts an example of a processing apparatus, shown as the system500, according to embodiments of the disclosure. FIG. 5 in particularpresents a top plan view (X-Y plane) of the system 500. The system 500may be especially useful or dedicated for performing a substrate dopingprocess employing helium implantation at elevated temperatures asdisclosed hereinabove. The system 500 may be configured as a clustertool, including a load lock 502 and transfer chamber 504 to transportsubstrates 520 to various processing chambers. An advantage of using acluster tool to perform multiple operations is the avoidance of breakingvacuum between operations, meaning substrates are not exposed to ambientatmosphere (outside the cluster tool) between operations, where theindividual operations may be performed under vacuum, under low pressure,or under controlled pressures of designated gases. The system 500 mayinclude an etch chamber 506 to perform substrate cleaning, such asremoving a native oxide layer. The etch chamber 506 may be coupled to agaseous etchant source 532, where the etch chamber 506 generates a hightemperature plasma etch species to etch material from the substrate, oremploys other gaseous etchant to etch the substrate in some embodiments.Examples of a plasma etch species include hydrogen, NF₃, Cl₂, and otherknown active etch chemistries, especially useful for etching oxides.

The system 500 may further include a hot implant chamber 508 coupled toa helium source 518. In various embodiments the hot implant chamber 508may provide a helium plasma generating helium ions of an appropriateenergy for implantation into the substrate 520. The hot implant chamber508 may include a known plasma generator such as an RF (radio frequency)coil, and may be configured as a plasma immersion system in someembodiments. In other embodiments the hot implant chamber 508 may beconfigured with a separate plasma chamber generating a plasma, andhaving an extraction system forming an ion beam, where the ion beam isdirected to the substrate 520. The hot implant chamber 508 may includeany appropriate heater, shown as heater 526, such as a radiative heater,resistance heater, induction heater, or other heater.

The system 500 may also include a dopant deposition chamber 510 coupledto a dopant source 522, where dopant deposition is carried out bychemical vapor deposition processes arranged according to knowntechniques. The system 500 may also include a capping layer chamber 512coupled to a capping material source 524, where a process for depositinga capping layer such as silicon nitride is performed. Appropriateprocesses for capping layer chamber 512 may be CVD plasma CVD, physicalvapor deposition, or other deposition technique. Examples of a cappinglayer source include a liquid or gas source(s) providing the appropriatematerial (e.g. Si, N) or a solid target material providing theappropriate material. The system 500 may also include an annealingchamber 514 having a heater 528, where high temperature annealing, suchas annealing above 800° C., is carried out. In some examples, theannealing chamber 514 may be configured for rapid thermal annealing byusing lamps or other appropriate components. During a doping process,the substrate 520 may be transferred between the various processchambers of the system 500 via transfer chamber 504 without beingexposed to outside ambient.

FIG. 6 depicts an exemplary process flow 600 according to embodiments ofthe disclosure. At block 602 the operation is performed of implanting adose of helium species into substrate through surface of substrate atimplant temperature greater than 300° C. In particular embodiments, theimplant temperature may range between 400° C. and 500° C.

At block 604, the operation is performed of depositing a doping layercontaining a dopant on the surface of the substrate. In some embodimentsa thickness of the doping layer may range between 0.1 nm and 3 nm. Atblock 606 the operation is performed of depositing a capping layer onthe substrate after the implanting. At block 608, the operation isperformed of annealing the substrate at an anneal temperature, where theanneal temperature is greater than the implant temperature. Examples ofappropriate anneal temperature include the range of 800° C. to 1000° C.In some embodiments, the anneal temperature may represent the peaktemperature of a rapid thermal anneal process where the duration at peakis less than 10 seconds and in some cases 1 second or less.

The present embodiments provide the advantage of a technique to increasedopant diffusion into a substrate from a deposited layer, while notamorphizing a substrate being implanted. This avoidance of amorphizingthe substrate may lead to the further advantage of increased activationof dopant after annealing is performed. The present embodiments alsoprovide the further advantage of scalability of doping processes usingdeposited layers in non-planar devices, such as finFETs.

The present disclosure is not to be limited in scope by the specificembodiments described herein. Indeed, other various embodiments of andmodifications to the present disclosure, in addition to those describedherein, will be apparent to those of ordinary skill in the art from theforegoing description and accompanying drawings. Thus, such otherembodiments and modifications are in the tended to fall within the scopeof the present disclosure. Furthermore, while the present disclosure hasbeen described herein in the context of a particular implementation in aparticular environment for a particular purpose, those of ordinary skillin the art will recognize the usefulness of the present embodiments isnot limited thereto and the present embodiments may be beneficiallyimplemented in any number of environments for any number of purposes.Thus, the claims set forth below are to be construed in view of the fullbreadth and spirit of the present disclosure as described herein.

What is claimed is:
 1. A system, comprising: an etch chamber, arrangedto process a substrate, the etch chamber comprising a plasma chamber; atransfer chamber coupled to the etch chamber; a dopant depositionchamber, the dopant deposition chamber coupled to the transfer chamberand further coupled to a dopant source, the dopant deposition chamberconfigured to perform a chemical vapor deposition of a dopant species;and a capping layer chamber, coupled to the transfer chamber, thecapping layer chamber comprising a chemical vapor deposition chamber, aplasma chemical vapor deposition chamber, or physical vapor depositionchamber.
 2. The system of claim 1, the capping layer chamber beingfurther coupled to a capping material source, the capping materialsource comprising a liquid source or a gas source.
 3. The system ofclaim 2, the capping material source comprising a source of silicon, asource of nitrogen, or a source of both silicon and nitrogen.
 4. Thesystem of claim 1, the dopant source comprising a source of arsenic,boron, phosphorous, or silicon.
 5. The system of claim 1, wherein thetransfer chamber is arranged to transfer the substrate between the etchchamber, the dopant deposition chamber, and the capping layer chamber,while not breaking vacuum.
 6. The system of claim 1, further comprisinga hot implant chamber, coupled to a helium source, the hot implantchamber being further coupled to the transfer chamber, wherein thetransfer chamber is arranged to transfer the substrate between the etchchamber, the hot implant chamber, the dopant deposition chamber, and thecapping layer chamber, while not breaking vacuum.
 7. The system of claim6, the hot implant chamber comprising: a plasma generator, generatinghelium ions, the helium ions comprising an energy of 200 eV to 5000 eV;and a substrate heater generating a substrate temperature of 300° C. orgreater.
 8. The system of claim 1, further comprising: an annealingchamber, coupled to the transfer chamber and having a heater generatinga substrate temperature of greater than 300° C., wherein the transferchamber is arranged to transfer the substrate between the etch chamber,the annealing chamber, the dopant deposition chamber, and the cappinglayer chamber, while not breaking vacuum.
 9. The system of claim 6,further comprising: an annealing chamber, coupled to the transferchamber and having a heater generating a substrate temperature ofgreater than 300° C., wherein the transfer chamber is arranged totransfer the substrate between the etch chamber, the hot implantchamber, the dopant deposition chamber, the capping layer chamber, andthe annealing chamber, while not breaking vacuum.
 10. A method of dopinga substrate, comprising: cleaning the substrate in an etch chamber of acluster tool; moving the substrate from the etch chamber to a dopantdeposition chamber of the cluster tool via a transfer chamber, while notbreaking vacuum; depositing a dopant on the substrate in the dopantdeposition chamber; moving the substrate to a capping layer chamber ofthe cluster tool via the transfer chamber, while not breaking vacuum;and depositing a capping layer on the substrate in the capping layerchamber.
 11. The method of claim 10, further comprising directing a doseof a helium species into the substrate through a surface of thesubstrate at an implant temperature of 300° C. or greater, before thedepositing the capping layer.
 12. The method of claim 11, wherein thedirecting the dose of the helium species takes place before thedepositing the dopant.
 13. The method of claim 11, wherein the directingthe dose of the helium species takes place after the depositing thedopant.
 14. The method of claim 11, wherein the directing the dose ofhelium takes place in a hot implant chamber, the method furthercomprising: transferring the substrate between the dopant depositionchamber and the hot implant chamber via the transfer chamber, while notbreaking vacuum between the directing the dose of the helium species andthe depositing the dopant.
 15. The method of claim 10, furthercomprising annealing the substrate at an anneal temperature, the annealtemperature being greater than the implant temperature, after thedepositing the capping layer.
 16. The method of claim 15, wherein theannealing the substrate takes place in an anneal chamber, the methodfurther comprising: transferring the substrate between the dopantdeposition chamber and the anneal chamber via the transfer chamber,while not breaking vacuum between the depositing the capping layer andthe annealing the substrate.
 17. The method of claim 16, furthercomprising directing a dose of a helium species into the substratethrough a surface of the substrate at an implant temperature of 300° C.or greater, before the depositing the capping layer, wherein thedirecting the dose of helium takes place in a hot implant chamber. 18.The method of claim 17, further comprising: transferring the substratebetween the capping layer deposition chamber and the hot implant chambervia the transfer chamber, while not breaking vacuum between thedirecting the dose of the helium species and the depositing the dopant.